1. Field of the Invention
The present invention relates to a light source device and a projector provided with the light source device.
2. Description of the Related Art
Nowadays, data projectors are often used as image projecting devices for projecting images, such as displays of personal computers, video images and, images of image data stored in memory cards, on screens. Each of these projectors gathers light projected from light sources on a micromirror display device called a digital micromirror device (DMD®) or a liquid crystal display panel, to display color images on a screen.
Heretofore, in this type of projector, a discharge lamp having a high luminance has been mainly used as a light source, but in recent years, there have been made developments and suggestions of employing a light emitting diode, a laser diode, an organic EL or a fluorescent material as the light source. For example, in Jpn. Pat, Appln. KOKAI Publication No. 2011-13320, a light source device has been suggested which emits blue light obtained by dispersing an excitation light from a laser light source for emitting the excitation light having a blue wavelength, red light from a red color emitting diode for emitting the red light, and green light from a fluorescent material for emitting the green light by receiving the excitation light from the laser light source. In this light source device, a dichroic mirror is used which can transmit or reflect an arbitrary wavelength, to synthesize the blue light, the green light and the red light from the respective light sources on one image display device.
As described above, in the case of the light source device in which the light obtained by synthesizing light having different wavelengths is applied to the image display device, the dichroic mirror having characteristics of reflecting and transmitting a light of each wavelength is required. In the dichroic mirror, however, a transmittancy is poorer than an untreated glass and a reflectance is poorer than a total reflection mirror, owing to properties of a dichroic film to be used. Therefore, there is the problem that each time the light is transmitted and reflected, optical efficiency deteriorates. As a result of the loss of light by this dichroic mirror, the amount of light applied to the image display device from the light source device decreases. Consequently, an image projected from the projector is disadvantageously dark.